Simultaneous electrochemical immunosensing of alpha-fetoprotein and prostate specific antigen using a glassy carbon electrode modified with gold nanoparticle-coated silica nanospheres and decorated with Azure A or ferrocenecarboxylic acid

Progress and Outlook on Electrochemical Sensing of Lung Cancer Biomarkers

Electrochemical biosensors have emerged as powerful tools for the ultrasensitive detection of lung cancer biomarkers like carcinoembryonic antigen (CEA), neuron-specific enolase (NSE), and alpha fetoprotein (AFP). This review comprehensively discusses the progress and potential of nanocomposite-based electrochemical biosensors for early lung cancer diagnosis and prognosis. By integrating nanomaterials like graphene, metal nanoparticles, and conducting polymers, these sensors have achieved clinically relevant detection limits in the fg/mL to pg/mL range. We highlight the key role of nanomaterial functionalization in enhancing sensitivity, specificity, and antifouling properties. This review also examines challenges related to reproducibility and clinical translation, emphasizing the need for standardization of fabrication protocols and robust validation studies. With the rapid growth in understanding lung cancer biomarkers and innovations in sensor design, nanocomposite electrochemical biosensors hold immense potential for point-of-care lung cancer screening and personalized therapy guidance. Realizing this goal will require strategic collaboration among material scientists, engineers, and clinicians to address technical and practical hurdles. Overall, this work provides valuable insight for developing next-generation smart diagnostic devices to combat the high mortality of lung cancer.

Adriamycin coated silica microspheres as labels for cancer biomarker alpha-fetoprotein detection

Adriamycin (ADM)-coated silica microspheres as a label for the sensitive detection of a cancer biomarker alpha-fetoprotein (AFP) was reported. Silica microspheres (SiO2 MSs) were employed as the carrier for the immobilization of gold nanoparticles (Au NPs), secondary antibody (Ab2) and ADM (denote: ADM@Au NPs@SiO2 MS/Ab2) as labels. In the presence of AFP, the labels were captured on the surface of the Au NP-reduced graphene oxide (rGO) (Au NP-rGO) nanocomposites to form a sandwich structure vs. the specific recognition of antibody-antigen. In a pH 7.4 phosphate buffer solution, a well-defined peak of ADM at about -0.70 V (vs. SCE) was recorded via differential pulse voltammetry, the peak intensity of which was related to the concentration of AFP. Under optimal experimental conditions, the immunoassay exhibited a wide linear range (0.5 pg mL-1 to 75 ng mL-1) and low limit of detection (0.17 pg mL-1). Further, the immunoassay was evaluated for serum samples, which gave satisfactory results.

Electrochemical prostate-specific antigen biosensors based on electroconductive nanomaterials and polymers

Prostate cancer (PCa), the second most malignant neoplasm in men, is also the fifth leading cause of cancer-related deaths in men globally. Unfortunately, this malignancy remains largely asymptomatic until late-stage emergence when treatment is limited due to the lack of effective metastatic PCa therapeutics. Due to these limitations, early PCa detection through prostate-specific antigen (PSA) screening has become increasingly important, resulting in a more than 50% decrease in mortality. Conventional assays for PSA detection, such as enzyme-linked immunosorbent assay (ELISA), are labor intensive, relatively expensive, operator-dependent and do not provide adequate sensitivity. Electrochemical biosensors overcome these limitations because they are rapid, cost-effective, simple to use and ultrasensitive. This article reviews electrochemical PSA biosensors using electroconductive nanomaterials such as carbon-, metal-, metal oxide- and peptide-based nanostructures, as well as polymers to significantly improve conductivity and enhance sensitivity. Challenges associated with the development of these devices are discussed thus providing additional insight into their analytic strength as well as their potential use in early PCa detection.

Fabrication of a sensitive label free electrochemical immunosensor for detection of prostate specific antigen using functionalized multi-walled carbon nanotubes/polyaniline/AuNPs

The aim of this research is to introduce a novel label free electrochemical immunosensor based on glassy carbon electrode (GCE) modified with carboxylated carbon nanotubes (COOH-MWCNTs)/polyaniline (PANI)/gold nanoparticles (AuNPs) for the detection of prostate specific antigen (PSA). The AuNPs were utilized as a connector for PSA antibody immobilization through NH₂ groups on antibody. Investigations on modified electrode surface were performed by FT-IR spectrum, scanning electron microscope (SEM) and energy dispersive X-ray spectroscopy (EDS) to evaluate the synthesized nanocomposite and modified electrode surface. As a sensitive analytical method for the detection of PSA, differential pulse voltammetry (DPV) was employed in different ranges of antigen concentration, 1.66 ag·mL^-1 to 1.3 ng·mL^-1. In addition, the detection limit was obtained 0.5 pg·mL^-1, from the linear relationship between antigen concentration log and peak current. Also, the proposed immunosensor was carried out for the determination of PSA in human serum samples, indicating recoveries ranging from 92 to 104%. Finally, it should be noted that the reproducibility and specificity, along with the stability of the present immunosensor were examined, and satisfactory findings were obtained, thus proving it as a promising PSA immunosensor.

An electrochemical immunosensor for the prostate specific antigen based on the use of reduced graphene oxide decorated with gold nanoparticles

The authors describe an immunosensor for the prostate specific antigen (PSA). It was obtained by modifying a glassy carbon electrode (GCE) first modified with gold nanoparticles and then with reduced graphene oxide that was decorated with gold nanoparticles. The AuNPs on reduced graphene oxide provide a suitable surface for attachment of antibodies. On binding of the antigen, the square wave voltammetric signal (measured by using hexacyanoferrate as a probe) reduced. This method has two logarithmically linear analytical ranges that extend from 25 to 55 fg.mL^-1 and from 1 to 36 ng.mL^-1, respectively. The lowest detection limit is 2 pg.mL^-1. Electrochemical impedance spectroscopy was also carried out for PSA determination. EIS works in the 0.0018 to 41 ng.mL^-1 concentration range and has an LOD of 60 pg.mL^-1. This method was applied to the determination of PSA in (spiked) human serum samples. In order to survey the selectivity of immunosensor, determination of PSA was performed in human serum samples, and finally sensitivity and reproducibility were examined. Graphical abstract Facile label free immunosensor based on reduced graphene oxide decorated with gold nanoparticles for early diagnosis prostate cancer via ultrasensitive detection of PSA biomarker: application in human serum.

Electrochemical immunosensors - A powerful tool for analytical applications

Immunosensors are biosensors based on interactions between an antibody and antigen on a transducer surface. Either antibody or antigen can be the species immobilized on the transducer to detect antigen or antibody, respectively. Because of the strong binding forces between these biomolecules, immunosensors present high selectivity and very high sensitivity, making them very attractive for many applications in different science fields. Electrochemical immunosensors explore measurements of an electrical signal produced on an electrochemical transductor. This signal can be voltammetric, potentiometric, conductometric or impedimetric. Immunosensors utilizing electrochemical detection have been explored in several analyses since they are specific, simple, portable, and generally disposable and can carry out in situ or automated detection. This review addresses the potential of immunosensors destined for application in food and environmental analysis, and cancer biomarker diagnosis. Emphasis is given to the approaches that have been used for construction of electrochemical immunosensors. Additionally, the fundamentals of immunosensors, technology of transducers and nanomaterials and a general overview of the possible applications of electrochemical immunosensors to the food, environmental and diseases analysis fields are described.

Nanomaterial-based biosensors for detection of prostate specific antigen

Screening serum for the presence of prostate specific antigen (PSA) belongs to the most common approach for the detection of prostate cancer. This review (with 156 refs.) addresses recent developments in PSA detection based on the use of various kinds of nanomaterials. It starts with an introduction into the field, the significance of testing for PSA, and on current limitations. A first main section treats electrochemical biosensors for PSA, with subsections on methods based on the use of gold electrodes, graphene or graphene-oxide, carbon nanotubes, hybrid nanoparticles, and other types of nanoparticles. It also covers electrochemical methods based on the enzyme-like activity of PSA, on DNA-, aptamer- and biofuel cell-based methods, and on the detection of PSA via its glycan part. The next main section covers optical biosensors, with subsections on methods making use of surface plasmon resonance (SPR), localized SPR and plasmonic ELISA-like schemes. This is followed by subsections on methods based on the use of fiber optics, fluorescence, chemiluminescence, Raman scattering and SERS, electrochemiluminescence and cantilever-based methods. The most sensitive biosensors are the electrochemical ones, with lowest limits of detection (down to attomolar concentrations), followed by mass cantilever sensing and electrochemilumenescent strategies. Optical biosensors show lower performance, but are still more sensitive compared to standard ELISA. The most commonly applied nanomaterials are metal and carbon-based ones and their hybrid composites used for different amplification strategies. The most attractive sensing schemes are summarized in a Table. The review ends with a section on conclusions and perspectives.

Fluorescence and Scattering Light Cross Correlation Spectroscopy and Its Applications in Homogeneous Immunoassay

In this work, we propose fluorescence and scattering light cross-correlation spectroscopy (FSCCS) based on laser confocal configuration using silver nanoparticle (SNPs) and Alexa Fluor 488 (Alexa) as probe pairs. FSCCS is a single molecule (particle) method, and its principle is similar to that of fluorescence cross-correlation spectroscopy (FCCS). We established the setup of FSCCS using single wavelength laser and developed an immunoassay model of FSCCS. The reliability and adaptability of FSCCS method were evaluated by homogeneous sandwich immunoassay mode. In the study, liver cancer biomarker alpha-fetoprotein (AFP) was used as an assay model, two different antibodies were labeled with SNPs and fluorophore Alexa Fluor 488, respectively. In the optimal conditions, the linear range of AFP covers 5 pM to 580 pM and the detection limit is 3.1 pM. This method was successfully applied for direct determination of AFP levels in human serum samples, and the obtained results were in good agreement with data obtained via ELISAs. The advantage of this method lies in its simplicity, attractive SNPs probes, high sensitivity and selectivity and high efficiency. We believe that FSCCS method exhibits promising potential applications in homogeneous bioassays and study on the molecular interaction and nanoparticle-molecule interaction.

RNA aptamer-based electrochemical aptasensor for C-reactive protein detection using functionalized silica microspheres as immunoprobes

C-reactive protein (CRP) is a widely accepted biomarker of cardiovascular disease and inflammation. In this study, a RNA aptamer-based electrochemical sandwich type aptasensor for CRP detection was described using the functionalized silica microspheres as immunoprobes. Silica microspheres (Si MSs), which have good monodispersity and uniform shape, were firstly synthesized. The silica microspheres functionlized with gold nanoparticles (Au NPs) provided large surface area for immobilizing signal molecules (Zinc ions, Zn²⁺) and antibodies (Ab). RNA aptamers, which were specific recognized to CRP, were assembled on the surface of Au NPs modified electrode via gold-sulfur affinity. In the presence of CRP, a sandwich structure of aptamer-CRP-immunoprobe was formed. Square wave voltammetry (SWV) was employed to record the sensing signal, and a clearly reductive peak corresponding to Zn²⁺ at about -1.16V (vs. SCE) was obtained. Under optimal conditions, the aptasensor showed wide linear range (0.005ngmL^-1 to 125ngmL^-1) and low detection limit (0.0017ngmL^-1 at a signal-to-noise ratio of 3). Some possible interfering substance was also investigated, and the results obtained showed that the aptasensor possessed good selectivity. When the aptasensor was applied to real serum samples analysis, the satisfied results were obtained, indicating that the aptasensor possessed potential real application ability.

Ultrasensitive Multiplexed Immunoassay for Tumor Biomarkers Based on DNA Hybridization Chain Reaction Amplifying Signal

In this work, a novel electrochemical immunoassay protocol has been reported for simultaneous determination of multiple tumor biomarkers based on DNA hybridization chain reaction (HCR) for signal amplification. Alpha-fetoprotein (AFP) and prostate specific antigen (PSA) were selected as model biomarkers. The immunoassay protocol contained primary antibodies immobilized on gold nanoparticles (Au NPs), secondary antibodies conjugated with DNA concatemer from HCR of primer, auxiliary probe, and signal probe labeled with signal molecules (methyleneblue (MB) and ferrocene (Fc)). In the presence of target biomarkers, the sandwich immunocomplex was formed between the primary antibodies and secondary antibodies bioconjugates carrying numerous signal molecules. As a result, two well-resolved reduction peaks, one was at -0.35 V (corresponding to MB) and other was at 0.33 V (corresponding to Fc; both vs SCE), were obtained in differential pulse voltammetry, and peak currents changed were related to the level of biomarkers. Under optimal conditions, the electrochemical immunoassay exhibited a wide linear response range (0.5 pg mL(-1) to 50 ng mL(-1)) and low detection limits (PSA, 0.17 pg mL(-1); AFP, 0.25 pg mL(-1)) (at S/N = 3). In addition, the immunoassay was evaluated by analyzing simulate human serum sample, and the recoveries obtained were within 99.4-107.6% for PSA and 97.9-108.2% for AFP, indicating the immnuoassay could be applied to the simultaneous detection of AFP and PSA in human serum samples.